In most soils iron is abundantly present. Nevertheless, enormous acreages of agricultural land in the U.S. lack an adequate supply of iron in a form that is useful for the growth of the plants that are commonly raised there. In Western states, for example, it is estimated that more than 12 million acres (about 5% of the total cultivated acreage in 22 states west of the Mississippi River) are deficient in available iron.
The deficiency of available iron adversely affects plant growth generally by retarding foliage, flowering and seed production. This is often manifested in the growing plant as a sickly yellow-leaf condition known as "chlorosis."